[old republic]

Lincoln suspended Habeas corpus without Congressional Approval which is unconstitutional.

Congress later retroactively approved it but that could be construed as an ex post facto law which is also unconstitutional.

[M. Espinola]

It was unconstitutional to rip the United States in two, triggered by pro-slavery's "Confederacy Inc." plunging the nation into full scale civil war. A civil war the Confederate insurrectionists lost.